U.S. Pat. No. 5,185,351 describes processes for the preparation of imidazole compounds, in particular the preparation of eprosartan. Although the processes described in this patent produce the imidazoles claimed therein, there was a need to improve these processes when preparing compounds, such as eprosartan, on a commercial scale.
It has now been found that eprosartan can be prepared in three stages. These stages are: (Stage.dagger.1) the regioselective protection of 2-n-butyl4-formylimidazole; (Stage.dagger.2) the reaction between the product from Stage.dagger.1 and (2-thienyimethyl)-propanedioic acid, mono-C.sub.1-4 alkyl ester; and (Stage.dagger.3) quaternary salt formation, followed by a basic work-up and an acidification. The efficiency of this synthetic sequence and the quality and yield of eprosartan are particularly important when preparing said product on a large scale for therapeutic use.